Cognitive Factors Underlying Social Communication of Adults with Traumatic Brain Injury Each year approximately 125,000 Americans will sustain a traumatic brain injury (TBI) from which they are expected to suffer lifelong disability [2]. Of the myriad effects associated with moderate-to-severe TBI, social outcomes are among the most penalizing and can include the loss of friendships and social isolation [3]. Research has shown that social communication problems contribute significantly to these negative social outcomes [4] and are therefore important rehabilitation targets [5]. Despite the severe consequences of social communication impairments, the underlying mechanisms of these deficits remain poorly understood. Research has linked social communication impairments in adults with TBI to two cognitive processes that are frequently impaired in this population: theory of mind (ToM) and executive functioning (EF) [6-9]. Despite evidence of a likely association between these processes, it is unclear whether these relationships are correlational or causal in nature. The proposed study will investigate both the underlying cognitive mechanisms and social consequences of social communication problems for adults with TBI with three specific aims. The first aim of the proposed study is to investigate the effect of ToM demand on social communication performance of adults with TBI. It is predicted that adults with TBI will fail to increase the frequency with which they use words that reflect ToM (i.e. mental state terms) from a low-ToM discourse condition to a high-ToM discourse condition relative to comparison participants (CPs). The second aim of the proposed research is to investigate the effect of EF demand on social communication performance of adults with TBI. It is hypothesized that the frequency of social communication errors committed by adults with TBI will be greater in a high-EF condition relative to in a low-EF condition. EF demand is expected to have a significantly greater effect for adults with TBI. The third aim of the proposed study is to determine the relationship between social communication problems in adults with TBI and how their discourse is judged by naive raters. It is predicted that the degree of increase in mental state terms from the low- to high-ToM condition will be positively associated with naive raters' judgments while it is expected that the change in frequency of social communication errors from the low- to high-EF condition will be inversely associated with naive raters' judgments of social acceptability and appropriateness in adults with TBI. The proposed research will provide important information regarding the underlying cognitive mechanisms of social communication impairments of adults with TBI as well as the real-world consequences of these impairments. Findings of this study have a strong potential to inform future treatment of social communication impairments in adults with TBI. PUBLIC HEALTH RELEVANCE: Following moderate-to-severe traumatic brain injury (TBI) individuals frequently experience many negative social outcomes that have been associated with poor social communication. The proposed research will investigate how cognitive processing demands affect social communication in adults with TBI with the long-term goal of using this gained knowledge to help direct the development of more effective treatments for social communication impairments of adults with TBI.